Stelletta lactea

Carter, 1871b

Species Overview

Stelletta lactea Carter, 1871b is a white massive crust with rough surface, provided with pore fields. It is apparently quite rare, having been recorded only a few times from the south coast of Britain and the west coasts of France and Spain.

Taxonomic Description

Colour: White.
Shape, size, surface and consistency: Massive, spreading, insinuating in crevices and small holes in shells and rocks. Surface contours follow that of the substrate. Large, gaping, flush oscules. Pores concentrated in rounded fields. Rough to the touch. Consistency hard outside, soft and crumbly inside.
Spicules: Megascleres : Huge oxeas, fusiform, slightly curved, 1250 µm; orthotriaenes: 825 µm; dichotriaenes: 825 µm.
Microscleres : Oxyasters, small, with numerous rather blunt rays, but rather variable: 12 µm; trichodragmas: 25 µm long.
Skeleton: Cortex thin (clearly thinner than in S . grubii ), charged at the surface with an abundant layer of asters carried by the cladi of the triaenes. Cortical skeleton traversed by bundles of oxeas, which become irregular towards the interior.
Ecology: Shallow-water, in crevices and small holes, in rock pools; elsewhere down to 500 m.
Distribution: W Ireland, SW England, Normandy, Bretagne, Galicia; Azores.
Etymology: Lacteus (Latin) = of milk, referring to the colour.
Type specimen information: The type is in the Natural History Museum, London.

Remarks

Although Stephens (1912) reports this species as "fairly common" it is ill-known. Reliable descriptions date back from the previous century, although its occurrence is mentioned in later faunal lists. Its distinction from sympatric Stelletta species such as the common S . grubii is rather easily made when spicules are examined microscopically: a single category of euasters and the trichodragmas are distinctive. The trichodragmas are shared with Dragmastra normani Sollas, but that has pro-and anatriaenes, and much longer oxeas.
Source: Topsent, 1894.